diff --git a/src/rustdoc-json-types/lib.rs b/src/rustdoc-json-types/lib.rs
index e67e17a73cb73..a92f3ded77466 100644
--- a/src/rustdoc-json-types/lib.rs
+++ b/src/rustdoc-json-types/lib.rs
@@ -61,6 +61,13 @@ pub struct Crate {
 #[derive(Clone, Debug, PartialEq, Eq, Hash, Serialize, Deserialize)]
 pub struct ExternalCrate {
     /// The name of the crate.
+    ///
+    /// Note: This is the [*crate* name][crate-name], which may not be the same as the
+    /// [*package* name][package-name]. For example, for <https://crates.io/crates/regex-syntax>,
+    /// this field will be `regex_syntax` (which uses an `_`, not a `-`).
+    ///
+    /// [crate-name]: https://doc.rust-lang.org/stable/cargo/reference/cargo-targets.html#the-name-field
+    /// [package-name]: https://doc.rust-lang.org/stable/cargo/reference/manifest.html#the-name-field
     pub name: String,
     /// The root URL at which the crate's documentation lives.
     pub html_root_url: Option<String>,